1. Field of the Invention
The present invention relates generally to incremental software updating, and more specifically to a system and method for using an automated, multi-tiered approach to performing incremental software updates.
2. Description of Background Art
Some computer software publishers update their software "applications" (computer programs and data files associated with the programs) frequently. For some types of software applications, such as virus protection software, these updates are particularly frequent. Virus protection software applications are designed to detect computer viruses on a computer system, and may also remove viruses which are found. An example of such a software application is Norton Anti-Virus, published by Symantec Corporation of Cupertino, Calif. Because these virus protection software applications rely on data about specific viruses, and new viruses are constantly being written to avoid current virus detection capabilities, it is necessary to update virus protection software applications on a regular basis to account for the newest viruses. Frequent updating of data files is also necessary for some database publishers, who must put up-to-date information in their databases, and remove obsolete information therefrom. Periodic updating of general software applications to expand capabilities and eliminate "bugs" is also common.
Currently, several methods are used to update software applications. The simplest of these is to distribute one entire software application to replace an older one. This method, the "full update" method, is simple, but expensive and inconvenient. Typically the software is distributed on some type of removable media, such as floppy disks or CD-ROMs, which are costly to produce and distribute. The time an end user must wait for the removable medium to arrive and the time it takes for the software application to install itself on a computer system are inconvenient. This inconvenience is compounded where updates occur frequently. Because of the large size of software applications it is generally not feasible to distribute such updates over computer networks, such as the Internet. When full updates are distributed over the Internet, they often cause such high loads on servers that other users suffer slow-downs on the network, and the servers have trouble meeting the demands.
In order to bypass many of the problems associated with this type of software updating, some software publishers distribute "incremental updates." These updates do not contain entire software applications, but rather only that information necessary to transform a given version of a software application to a newer version. Among the methods available to perform such incremental software updating is binary patching, performed by programs such as RTPatch, published by Pocket Soft, Inc. A binary patcher replaces only those binary bits of a software application which are different in a newer version. Because most software updates involve changes to only a small portion of a software application, a binary patcher needs, in addition to the old software application, only a small data file including the differences between the two versions. The smaller data files distributed for a binary patch update are often less than 1% of the size of a full update, taking advantage of the large amount of redundancy in the two versions.
The use of incremental update methods allows for smaller updates which can be distributed by means that are not conducive to the distribution of full updates, such as distribution over the Internet. The smaller incremental updates also make distribution by floppy disk more feasible where a full update would have required many disks, and an incremental update may require only one. However, incremental update methods introduce another problem: the incremental update is specifically useful for updating only one particular version of a software application to another particular version. When updates occur frequently, as with virus protection software applications, end users may often update from an arbitrarily old version to the newest version, skipping over several previously released versions. An incremental update for the newest version of a software application will update only from the most recent version, however.
One solution to this problem has been for software publishers to group a number of binary patch data files together into one distribution. The user of an arbitrarily old version can then apply each incremental update, one at a time, to update to the newest version. However, the number of incremental updates may be large, due to the fact that the grouping covers a large number of versions. The benefits of smaller distributed update files begin to disappear, as the size of the grouped-together incremental updates grows. This method of updating applications can also be cumbersome, as a series of update patches need to be selected from the group and applied to the software application one after another.
Another solution to the problem of incremental update version-specificity has been to create a unique patch file for transforming every previous version of the application to the most current version. Some users may not wish to update their software applications to the most current version, however, for a number of reasons. Some may be within a corporate setting, where an information services department allows updates only to versions it has had a chance to test and approve. Others may have older computer systems which do not support the increased resource requirements of the newest version of an application. For these reasons, publishers of software updates using this method must generally keep updates available from every previous version of an application to a large number of more recent versions. This results in a geometrically growing number of update patch files to produce, store and maintain for users. In the case of publishers who update their applications frequently, such as publishers of virus-protection software applications, this may quickly become untenable.
One alternative to the methods described above is the use of "push" technology, in which servers maintain databases of what versions of a software application each user has. The servers then send the necessary updates to each user, as they become available. This system requires "smart" servers, however, to monitor user configurations, determine what each user needs, and send the appropriate update information. This results in a server-intensive system which can cause a drain on server resources comparable to that experienced in the full update scheme, when many users are simultaneously requesting full updates.
What is needed is a system for updating software applications from an arbitrary first version to an arbitrary second version which does not require a large amount of information to be stored and maintained by a software publisher, does not require the user to acquire a large amount of data to perform such an update, and does not require the use of "smart" servers.